You have to visit unknown when you're in LA *nudge nudge*
definitely check out Amoeba. Fucking amazing store. You'll blow all of your money there.
as far as metal shows in LA go,
http://www.moshking.com/ is where you want to check.
if you're staying near Amoeba, that means you'll be in hollywood/downtownish. Walk down Hollywood Blvd and check out the Chinese Theater and all the freaks in front of it. Walk by the Scientology headquarters and get harassed.
Go check out the Getty museum...it's an amazing art museum (if you and the Mrs are art fans)